Mutual remediation of effluents of petroleum production

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/144,665 filed Jan. 14, 2009 and U.S. Provisional Patent Application Ser. No. 61/144,694 filed Jan. 14, 2009, and incorporates by reference the entirety of each thereof.

BACKGROUND

1. The Field of the Invention

This invention relates to oil and gas production and, more particularly, to novel systems and methods for environmental protection from, and remediation of, production materials and processes.

2. The Background Art

The production and transportation of petroleum resources, including oil and natural gas, often involves the introduction of emissions of substances considered pollutants into the natural environment. Often the production areas are in locations regarded as being particularly environmentally sensitive. Sources of pollutants include engines, heaters, flares, road surfaces, and production fluids themselves. Production water often contains dissolved solids (e.g., salts) that make it unsuitable for ordinary beneficial (e.g., agricultural, culinary, etc.) use or release directly into the environment. Hauling water to and from the production site usually requires extensive and expensive trucking over roads through environmentally sensitive areas. Similarly, large amounts of waste heat from numerous engines, heaters, burners, flares, or combinations thereof are released into that same sensitive environment. Any company or state with extensive fossil fuel reserves will have much at stake over these issues.

What is needed is a system and method to address the issues of effectively mitigating environmental impacts associated with fossil fuel development and production.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, in accordance with the invention as embodied and broadly described herein, a method and apparatus are disclosed in one embodiment of the present invention as including a source of combustion exhaust, a substantially horizontal “stack” acting also as a scrubber, and a recovery system. The recovery system may typically include a blower, a cyclone, a condenser, and various heat exchangers.

Saline production water is often available in the same location as flares, burners, heaters, engines and compressor stations. Basic design concepts have been developed for using production water to effectively scrub the emissions of volatile organic compounds, unburned hydrocarbons, combustion particulates, and sulfurous oxides. From these combustion sources, systems in accordance with the invention simultaneously put the waste heat from these combustion sources to beneficial use to evaporate production brine, thus reducing the volume of saline production water to be disposed of, in an environmentally responsible manner.

In many oil/gas fields, the quantities of waste heat available are not sufficient to process the amount of saline water produced in the same area. In such situations, the same design concepts provide for clean emission-scrubbed combustion of field gas to supplement any waste heat available. An efficient energy recovery system makes evaporation a cost effective way to dispose of the saline water with minimal environmental impact. In addition, the energy recovery system also returns a large fraction of the saline production water as clean distilled water.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which:

<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic perspective view of one embodiment of an apparatus in accordance with the invention;

<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic perspective view of an alternative embodiment of an apparatus in accordance with the invention;

<figref idrefs="DRAWINGS">FIG. 3</figref> is a schematic perspective view of the embodiment of <figref idrefs="DRAWINGS">FIG. 1</figref> augmented with a bank of heat exchangers;

<figref idrefs="DRAWINGS">FIG. 4</figref> is a schematic perspective view of an alternative embodiment of an apparatus in accordance with the invention, augmented with heat and moisture recycling heat exchangers;

<figref idrefs="DRAWINGS">FIG. 5</figref> is a schematic perspective view of the embodiment of <figref idrefs="DRAWINGS">FIG. 4</figref> with double walled scrubber recycling heat and moisture from the heat exchangers;

<figref idrefs="DRAWINGS">FIG. 6</figref> is an end cross-sectional view of one embodiment of passages of a heat exchanger in accordance with the invention;

<figref idrefs="DRAWINGS">FIG. 7</figref> is a top quarter perspective view of the heat exchanger of <figref idrefs="DRAWINGS">FIG. 6</figref>; and

<figref idrefs="DRAWINGS">FIG. 8</figref> is a side elevation view of the heat exchanger of <figref idrefs="DRAWINGS">FIGS. 6 and 7</figref> assembled with end manifolds.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be readily understood that the components of the present invention, as generally described and illustrated herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented here and in the Appendix attached hereto, is not intended to limit the scope of the invention, as claimed, but is merely representative of various embodiments of the invention.

Notwithstanding consolidation of multiple wells at a single production site, as well as various waste containment and site restoration, environmental impacts continue from the production of natural gas and oil. Typically, sources of particulate emissions include heaters used to reduced the viscosity of oil. Likewise, various motors or engines designed to run on petroleum byproducts such as “field gas” produce heat and hydrocarbon emissions. Meanwhile, production of small quantities of field gas in oil fields results in gas having to be flared off. Thus, flares and other sources contribute particulate and thermal emissions. The alternative to flaring is to release unburned hydrocarbons into the atmosphere. Even after burning or other remediation methods, unburned volatiles are still often returned into the environment intentionally or accidentally.

Heaters typically burn field gas to warm crude oil to reduce its viscosity for better handling. The high viscosity of crude oil is often responsible for high pumping costs. Pumping costs may be reduced by reducing viscosity of the oil. Some crude oil is so thick that it actually behaves as a thixotropic material. Also, as part of the separation process for separating water from oil, gas, or both heaters may be employed.

Engines used in oil fields and gas occur in two principal functions. Natural gas typically is compressed to increase the mass flow rate to collection points from the distribution networks at individual oil fields Likewise, crude oil must be pumped or otherwise transported from the well head to a collection point. Some wells produce little enough to transport it on trucks. Others produce sufficient volume to justify pumping from the well head to collection points. From collection points, crude oil may still be trucked or otherwise transported.

In any event, pumping requires drive motors. Thus, engines are integral to the transport of crude oil and natural gas. Meanwhile, production of oil requires pumps drawing oil from the earth. Moreover, drilling processes themselves rely on engines. Thus, whether driving a pump, compressor, generator, or drilling rig, engines are a burner of fuels, and a generator of thermal and other emissions.

Flares have been reduced in recent years but remain in several circumstances. Typically, if a field produces substantial quantities of natural gas, commercially significant volumes, then collection is developed and an infrastructure is put in place to do so. In other circumstances insufficient quantities may not justify collection and transport. In these circumstances, unsteady or gas may be flared off. Meanwhile, gas production may not be uniform. In such circumstances, periodic gas generation may require flaring. Thus, some amount of flaring of field gas is substantially unavoidable. However, the vision of a tall stack with a large, orange, sooty flame flaring at the top thereof creates public relations issues as well as legitimate environmental concerns.

Meanwhile, unburned volatiles existing in the process of producing natural gas and crude oil arise in several circumstances. For example, unburned volatiles may be part of the production water separated from oil and gas products. Meanwhile, various combustion processes (e.g., engines, heaters, etc.) may still pass unburned volatiles through. Unburned hydrocarbons, whether heavy or volatile, can result from heavy molecular chains that are not completely or efficiently broken down and combusted. Likewise, unburned volatiles may simply result from processes and equipment that burn at temperatures and in flow patterns that do not complete combustion of all volatiles. Meanwhile, volatiles can arise from other sources as well.

The result is tank batteries, sumps, holding ponds, possible exposure to leaks or breaks in containment structures, and the like. All of these may give rise to the need to handle unburned volatiles.

In summary, oil, gas, saline water, (production water), and the like are the typical fluids from oil and gas production. Since evaporation ponds, injection wells, and hauling are all subject to their own difficulties, an apparatus and method in accordance with the invention may augment the disposal of production water. Since containment, hauling, reinjection, evaporation, and the like all have risks and limits, an apparatus and method in accordance with the invention deals with production water at a wide variety of salinity values, net volumes, and so forth.

In various embodiments of apparatus and methods in accordance with the invention, production water is used to scrub oil and gas emissions in the field. Meanwhile, waste heat from combustion sources is used in evaporating production water. The production water vapor from evaporation may be dispersed into the atmosphere, or may be re-condensed as distilled water for use in systems that would otherwise not tolerate the water as a saline solution.

Referring to <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>, in one embodiment of an apparatus <b>10</b> or system <b>10</b> in accordance with the invention, a horizontal remediator <b>200</b> may act as an evaporator <b>200</b>, as a scrubber <b>200</b>, or both. The scubber-evaporator <b>200</b> relies on a blower <b>202</b> to draw a flow <b>204</b> of combustion emissions. Combustion emissions may exist, for example, as an exhaust stream <b>204</b> from a flare, a heater, an engine, or the like. A gas burner <b>206</b> device or region may hold a flame <b>207</b> burning field gas as a heat source or may augment combustion of unburned hydrocarbons (e.g., volatile organic compounds or VOCs) in the exhaust stream <b>204</b>, or may serve to do both.

Meanwhile, an upstream damper <b>208</b> on the flow <b>204</b> may be used to regulate the back pressure on the engine, burner, or other source feeding an exhaust stream into the system. A system of nozzles <b>210</b> optimized to effect evaporation of water injects an atomized spray <b>212</b> of production water (brine, typically) from a feed line <b>214</b> into the exhaust stream <b>204</b>. The system <b>10</b> typically contains salts, and recovers them from the exhaust stream <b>204</b> in a cyclone <b>216</b>. A blower <b>202</b> maintains a draw on the cyclone <b>216</b>. Feeding the exhaust stream <b>204</b> from a scrubbing “stack” <b>200</b>, oriented as a horizontal tube <b>201</b> intersecting at the edge of the cyclone <b>216</b>, promotes the separation of solids, liquids, or both from the vapor and gases, by the cyclone <b>216</b>.

In certain embodiments, a burner <b>206</b> may be installed as an integral part of the evaporation module <b>200</b> in accordance with the invention. In such an embodiment, the burner <b>206</b> may be installed in a separate or integrated conduit <b>218</b> fed by air flow regulated through a damper <b>208</b>. The flow <b>204</b> of combustion products is then transported through the conduit <b>218</b> to be directly intercepted by atomized sprays <b>212</b> of production water. Thereafter, the exhaust products, scrubbed by the liquids, together with the evaporated liquids (now vapors) and precipitated or in trained solids, may be sent into the cyclone <b>216</b> for separation.

Ultimately, the blower <b>202</b> draws the noncondensible gases and the vapors out, exhausting them to the atmosphere or a condenser. Salt as solids, heavy hydrocarbons, other particles scrubbed out, as well as liquids may remain behind, exiting the bottom <b>219</b> of the cyclone <b>216</b>, such as through a drain <b>220</b>, after being separated out by the cyclone <b>216</b>.

In the cyclone <b>216</b>, the flow <b>204</b> containing multiple phases such as noncondesible gases, vapors, liquids, and solids, is received as an incoming flow <b>222</b>. The incoming flow <b>222</b> tends to strike the wall <b>224</b> of the cyclone <b>216</b>, directing the flow <b>222</b> in a circumferential direction centripetal force moves heavier (denser) materials outward <b>226</b>, where they may strike the wall <b>224</b> and fall downward toward the bottom <b>219</b>. Lighter (less dense) materials, more easily accelerated by fluid drag of surrounding vapors and gases, move inward <b>228</b>. These less dense, more easily entrained, materials eventually follow a path <b>230</b> upward toward an outlet line <b>232</b> or conduit <b>232</b> evacuating the cyclone <b>216</b>.

The outlet line <b>232</b> feeds into an inlet <b>234</b> or inlet portion <b>234</b> receiving the noncondensible gases (oxygen, nitrogen, etc.), vapors (water, etc.) from the flow <b>204</b>. Thus, the discharge <b>236</b> from the blower <b>202</b> may pass into the atmosphere or into a device, such as a condenser, for further processing.

Not only does the damper <b>208</b> provide the opportunity to control back pressure on a heat source such as an engine, heater, flare, or the like, the injection nozzles <b>210</b> may be designed to provide repeatedly a cone of spray that will completely cover the cross section of the “stack” <b>200</b> formed by the conduit <b>218</b>. (The reference numeral <b>218</b> refers to conduits generally, and when used with a trailing letter indicates a specific instance thereof.) Thus, by spraying axially along a conduit (forward, backward, or both with respect to the exhaust flow) the flow <b>204</b> may pass through several conical curtains of spray <b>214</b> that effectively present a barrier across the entire cross section of the conduit <b>201</b> of the evaporator <b>200</b> or scrubber <b>200</b>. Spray <b>212</b> direction, velocity, particle size, chemical content, or the like may be optimized for scrubbing, evaporating, or both.

In some circumstances, the balance between scrubbing and evaporating may be accomplished by adjusting the length of the scrubber <b>200</b> to provide the needed quantity of evaporation as well as scrubbing required. Again, the damper <b>208</b> may also be used to optimized flows, balancing back pressure on the burner <b>206</b> (or engine, flare, heater, etc.) while also regulating the mixture of dry ambient air mixed into the exhaust flow <b>204</b>.

A secondary flame <b>207</b> or burner <b>206</b> for reacting or oxidizing unburned hydrocarbons or volatile organic compounds remaining in an exhaust stream <b>204</b> may be operated or installed according to need. If comparatively clean field gas, predominantly natural gas (e.g., methane), is available, the presence of volatile organic compounds may be manageable. By contrast, a diesel engine operating on a well site may release more particulate emissions and unburned volatile or non-volatile organic compounds. Likewise, burning field gas having a higher fraction of larger molecules than does methane, and perhaps some very large petroleum molecules entrained, may tend toward higher levels of volatile organic compounds in the exhaust.

Referring to <figref idrefs="DRAWINGS">FIG. 3</figref>, while continuing to refer generally to <figref idrefs="DRAWINGS">FIGS. 1-8</figref>, in one embodiment, a remediator device <b>200</b> acting as a scrubber <b>200</b>, evaporator <b>200</b>, or combination <b>200</b>, may also be combined with a recovery module <b>240</b>. The recovery module <b>240</b> may include one or more condensers <b>242</b> to recover water vapor as, effectively, distilled water. A discharge line <b>244</b> may send a flow <b>243</b> of the recycled condensate to feed the line <b>214</b> into the nozzles <b>210</b>. In certain embodiments, the condensers <b>242</b> may be oriented vertically, so air flows promote a natural chimney-effect buoyancy. For example, air flows <b>243</b>, drawn in and used to cool the water vapor and exhaust gases received from the blower <b>202</b>, will receive heat therefrom, tending to cause and upwardly rising flow <b>248</b> of scrubbed exhaust gases, water vapor, and ambient air as a result of the decreased density thereof out of the system <b>10</b>.

In certain embodiments, the blower <b>202</b> drawing on the cyclone <b>216</b> and the scrubber <b>200</b> or evaporator “stack”<b>200</b> may be configured to raise the pressure in the condensers <b>242</b>. Thus, the resulting, reduced, upstream pressure may promote evaporation in the scrubber <b>200</b> or evaporator <b>200</b>, as well as in the cyclone <b>216</b>. The increased pressure in the subsequent or downstream condenser system <b>242</b> beyond the blower promotes increased condensation.

The flow <b>243</b> in the line <b>244</b> fed from the condensers <b>242</b> is distilled water. Optionally, a makeup flow <b>249</b> of water may be required. The makeup flow <b>249</b> may pass through the line <b>245</b> into the feed line <b>214</b> to supply the nozzles <b>210</b>. The extent to which the flow <b>246</b> from the condenser <b>242</b> is insufficient to completely supply the scrubber <b>200</b> is driven by the net evaporation of water in the discharge flow <b>248</b>, as well as the drained brine exiting the cyclone <b>216</b> through the bottom drain <b>220</b>. The condensers <b>242</b> may be configured modularly in order to best match the flows <b>222</b>, <b>236</b>, <b>243</b> throughout the system <b>10</b>.

In general, flows <b>246</b> of ambient air may pass through the inlet <b>247</b> into a manifold <b>248</b> feeding the condensers <b>242</b>. Meanwhile, in a concurrent flow arrangement, passages feeding an exhaust flow <b>236</b> from the blower <b>202</b> run vertically, adjacent to passages feeding the ambient air flow <b>246</b> upward through the condensers <b>242</b>. Adjacency may be horizontal in a rectangular, circular, or other configuration. The illustrated embodiment relies on radially concentric, adjacent passages. Thus, cooled exhaust and warmed ambient air form the mixed flows <b>248</b> exiting the condensers <b>242</b>.

Referring to <figref idrefs="DRAWINGS">FIG. 4</figref>, and <figref idrefs="DRAWINGS">FIGS. 1-8</figref> generally, in other alternative embodiments, a heat recovery section <b>250</b> or module <b>250</b> may be added. The recovery module <b>250</b> may be connected by providing manifolds <b>252</b>, <b>254</b> on the inlet and outlet ends <b>256</b>, <b>258</b>, respectively, of one or more condensers <b>242</b> acting as heat exchangers <b>242</b>. For example, a counter-flow (or even a cross-flow) heat exchanger <b>242</b> may provide ambient air coming into an inlet <b>260</b>, passing through the heat exchangers <b>242</b>, and continuing onward toward an outlet <b>262</b>.

As seen in <figref idrefs="DRAWINGS">FIGS. 4 and 5</figref>, in certain embodiments, the outlet <b>262</b> may feed into a double-walled conduit <b>218</b>. For example, the scrubber <b>200</b> may have a double wall as illustrated in order to feed the output flow from the outlet <b>262</b> into an outer shell or annulus of the conduit <b>218</b>. The outer annulus of the conduit <b>218</b>, in turn, empties into the axially central portion of the conduit upstream of and feeding into the flame <b>207</b> of the burner <b>206</b> thereat. Thus, preheating uses heat and mass flows recaptured by the heat exchangers <b>242</b> and recycled into the exhaust flow <b>24</b> near the inlet to the scrubber <b>200</b>.

This ambient air flow <b>246</b> passes through one set of channels (e.g., the channels formed by the supporting, corrugated dividers in one annulus of the several concentric annuli) in the heat exchanger <b>242</b>. The corresponding heat transfer flow or opposing flow may travel in an opposite direction through radially adjacent annuli flanking the first. This corresponding or opposite flow, when implemented in a rectangular system, may run either parallel to or orthogonal to the channels or overall passages carrying scrubbed exhaust <b>236</b> exiting the blower <b>202</b>. Leaving the heat exchanger, the discharge <b>236</b> becomes an exiting flow <b>264</b> issuing from the exhaust outlet <b>266</b>.

Air and water may be preheated by a condenser <b>242</b> acting as a heat exchanger <b>242</b> recovering the sensible heat of gases, as well as the potentially substantial latent heat of vaporization out of the distilled water output from the condenser <b>242</b>. The outlet <b>262</b> passing pre-warmed ambient air into the evaporator <b>200</b> may connect to the conduit <b>201</b> of the evaporator <b>200</b> further upstream along the exhaust flow <b>204</b>. In either configuration, significant energy inputs and water (distilled)) may be recovered into the exhaust flow <b>204</b>. Thus, a certain portion of the heat may be continually added into the exhaust flow <b>204</b>, and yet be re-extracted prior to final exit of the exhaust flow <b>264</b> out of the system <b>10</b>.

Referring to <figref idrefs="DRAWINGS">FIG. 5</figref>, while continuing to refer generally to <figref idrefs="DRAWINGS">FIGS. 1-8</figref>, in other embodiments, waste heat from another device, such as a heater, engine, flare, or the like, outside the system <b>10</b>, may not be available. For example, remediation of production water may require burning field gas directly to evaporate water. Thus, in certain embodiments an apparatus <b>10</b> in accordance with the invention may burn field gas in a burner <b>206</b> creating the hot exhaust flow <b>204</b> for the specific purpose of evaporating water to be run through a evaporator <b>200</b> and cyclone <b>216</b>. Ultimately, the system <b>10</b> may condense a portion of the water back to distilled water.

By providing heat exchange as in the embodiment of <figref idrefs="DRAWINGS">FIG. 4</figref>, the system <b>10</b> may preheat air and water. Heat may be recovered from both the sensible heat recovered from the discharged flow <b>264</b> and the latent heat recovered from the condensed distilled water. Pressure increased in the condenser due to pressure from the blower <b>202</b> enhances condensation. The pressure drop in the evaporator <b>200</b>, due to the draw by the blower <b>202</b> demand for input enhances evaporation, as described hereinabove.

Referring to <figref idrefs="DRAWINGS">FIGS. 6-7</figref> while continuing to refer generally to certain to <figref idrefs="DRAWINGS">FIGS. 1-8</figref>, in certain embodiments, a condenser <b>242</b> may provide a flow of heat, exchanged through concentric cylinders <b>270</b> spaced apart. The spacers <b>272</b> themselves may take the form of corrugated metal sheets or the like. Thus, the spacers <b>272</b> may act as fins while supporting each annulus <b>274</b> between adjacent cylinders <b>240</b>, forming channels <b>276</b> between the fins.

Adjacent annuli <b>274</b> carry flows in opposite directions for counter-flow heat exchange. Accordingly, excellent thermal contact between the exhaust <b>236</b>, with its condensing vapors, and the cooling air receiving heat therefrom may be achieved. A structurally robust configuration results from essentially very thin materials, such as sheet metal, for example.

Referring to <figref idrefs="DRAWINGS">FIG. 8</figref>, while continuing to refer generally to <figref idrefs="DRAWINGS">FIGS. 1-7</figref>, such a heat exchanger <b>242</b>, using concentric tubular structures <b>270</b>, may be interfaced with a manifold <b>272</b>, <b>274</b>. Manifolds may be mechanically attached in fluid communication with the condensers <b>242</b> at either end. Passages in the manifolds <b>272</b>, <b>274</b> each provide access to only periodically occurring (e.g., typically alternating) annular spaces <b>274</b>.

For example, an ambient air flow <b>246</b> may enter an inlet <b>260</b> of the manifold <b>254</b>. Passing through the channels <b>276</b><i>a</i>, the air is heated by exhaust flows <b>204</b> in adjacent annuli <b>274</b><i>a</i>, <b>274</b><i>b</i>, radially adjacent channels <b>276</b>. Adjacency between annuli <b>274</b> each with its own set of channels <b>276</b> distributed circumferentially therearound, contributes to comparatively high rates of heat transfer therebetween, due to thin annular walls and the fin effect of the spacers <b>272</b>.

By the time the exhaust flow <b>264</b> exits the outlet <b>266</b>, it has released most of its heat into the ambient air flow <b>246</b>. The exact heat exchange and temperature changes depend upon the specific values of parameters such as thicknesses, hydraulic diameters, lengths, fluid properties, velocities, and so forth controlling heat transfer.

Moreover, a significant amount of latent heat from any water vapor condensed therein has also been so transferred. The manifolds <b>252</b>, <b>254</b> support distribution and collection of flows into distinct annuli <b>274</b> by having each inlet or outlet end of annulus <b>274</b> connect to a particular layer <b>278</b> of the respective manifold <b>252</b>, <b>254</b>.

Thus, various apparatus and methods in accordance with the invention may significantly reduce the environmental impact of saline water as well as that of chemical, thermal, particulate, and other exhaust emissions. To the extent that these processes can be balanced, a highly symbiotic relationship may exist between remediation of production water, remediation of organic compositions including VOCs, remediation of rejected heat, and remediation of combustion products.

Meanwhile, the tall stack, so familiar, with the flare of a production facility or refinery, may be laid down as a horizontal tube, less expensive to manufacture, easier to maintain, and easier to support. Meanwhile, stacks may have immediate and affirmative back pressure control by attachment of dampers. Meanwhile, scrubbing reduces emissions of volatile organic compounds, oxides of sulfur, particulates, and heat, while recovering heat, distilled water, or both to be recycled from saline production.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.